This invention relates an attachment for a saw. More specifically, this invention relates to an attachment for a reciprocating saw which enables the saw to be used more conveniently and safely to make cuts adjacent an interior corner of a room, or in similar situations there two planar surfaces meet forming an interior angle.
Workers engaged in the building and allied trades often make use of powered reciprocating saws, such as those sold under the Registered Trade Mark xe2x80x9cSAWZALLxe2x80x9d. Such reciprocating saws typically comprise a substantially cylindrical body having a diameter of about 10-15 cm. (about 4-6 inches) such that it can comfortably be supported on one hand. The body typically contains an electric motor (a pneumatic or other motor may also be used) which is arranged to reciprocate a drive head axially of the cylindrical body, this drive head being substantially centrally located on one end surface of the cylindrical body. The drive head is provided with blade attachment means so that a saw blade can be mounted on the drive head to reciprocate therewith. In some cases, to minimize the risk of damage to a wall or other surface being cut, and to increase operator safety, a guard is pivotally mounted on the cylindrical body at a point adjacent the drive head. Also to increase operator safety, a substantially frusto-cylindrical flexible skirt is mounted on the body surrounding the drive head, this skirt tapering outwardly as it extends from the drive head. The end of the body remote from the drive head is usually provided with a handle and with a power switch.
Although modem reciprocating saws are very useful and enable a worker to form saw cuts much more quickly than is possible with a hand saw, they do suffer from the problem that, because of the size of the housing, they cannot be used in their normal position (i.e., with the axis of the cylindrical housing lying in a plane perpendicular to the wall or other surface being cut, this plane containing the saw cut) when it is necessary to make a cut close to an interior corner, for example two walls meeting at right angles, or between a wall and a floor. To make such cuts, construction workers often bend the blades of such saw, so that the part of the blade making the cut still lies substantially perpendicular to the wall, while the cylindrical body lies at an acute angle to the wall, inclined away from the interior corner. Such bending of the saw blade renders it difficult to form a neat saw cut, since the blade will inherently attempt to straighten itself, thus forming a non-linear cut. More seriously, the bent blade some times fractures, resulting in damage to one or both surfaces forming the corner, and the risk of serious injury to the operator.
Attempts have been made to overcome the need to bend saw blades when cutting adjacent a corner. For example, U.S. Pat. No. 2,954,808 (Sweeney et al.) describes an offset attachment for a reciprocating saw. This attachment comprises a substantially Z-shaped member having a first section which engages the drive head, a second section which extends substantially normal to the first section and laterally of the axis of the body, so that the outer end of the second section is clear of the saw body, and a third section which extends from the outer end of the second section parallel to the first section and carries a saw blade. An extended support is rigidly mounted on both sides of the saw body and extends forwardly, being provided with a first surface which lies adjacent and parallel to the saw blade, and a second surface which can abut the wall or other surface being cut. However, this apparatus has serious disadvantages. One side of the saw blade is exposed along its entire length, and this exposed blade is potentially dangerous to an operator. Furthermore, since the support only contacts the wall on one side of the blade, the blade may tend to tilt away from the support. Finally, since the extended support is rigidly mounted on the saw body, when the saw is tilted at an angle to the surface being cut (as when starting a saw cut) only one edge of the second surface will contact the surface, which may result in damage to the surface.
Thus, there is a continuing need for an attachment which will all use of a reciprocating saw to make cuts adjacent and interior corner in a manner which promotes operator safety and minimizes the risk of damage to the walls or other surfaces forming the corner, and it is a primary object of this invention to fulfill this need.
Accordingly, this invention proves an attachment for a reciprocating saw, the saw having a body and a drive head arranged to reciprocate in one, axial direction. This attachment comprises an offset member having mounting means whereby it may be releasably mounted on the drive head, blade attachment means arranged for attachment of a saw blade thereto, and a lateral extension member extending between the mounting means and the blade attachment means such that when the mounting means are mounted on the drive head the lateral extension member will extend laterally of said axial direction and hold the blade attachment means clear of the saw body. The attachment also comprises a guard member having an engagement member provided with a substantially planar wall engaging surface adapted to engage a wall, and a slot extending from the wall engaging surface through the engagement member, the guard member also having guard mounting means whereby it may be pivotally mounted on the body of the saw at a point spaced from the drive head thereof, such that the wall engaging surface extends transversely of said axial direction, and such that a saw blade mounted on the blade attachment means will extend through the slot.
In saying that the lateral extension member holds the blade attachment means clear of the saw body, we mean that the blade can cut in a wall immediately adjacent an interior corner without the body of the saw contacting the other wall forming the corner. In strict geometric terms, the blade attachment means should hold the blade outside the volume defined by translating the saw body forwardly parallel to the direction of movement of the drive head.
In one preferred form of the attachment of the present invention, the offset member is substantially L-shaped and comprises a first limb bearing at its one end the mounting means, and a second limb attached to the opposed end of the first limb, extending substantially normal to the first limb and bearing the blade attachment means. Preferably, both the first and second limbs of the offset member are elongate, with the first limb extending substantially along said axial direction and the second limb extending substantially normal to said axial direction.
In the present attachment, the blade attachment means preferably comprises an auxiliary member capable of being releasably secured to the remaining portion of the offset member, the auxiliary member and the remaining portion of the offset member each being provided with a bearing surface such that the auxiliary member can be secured to the remaining portion of the offset member with a saw blade clamped between the two bearing surfaces.
In another preferred form of the attachment of the present invention, in addition to the engagement member, the guard member comprises an elongate extension piece bearing at one end the guard mounting means, the opposed end of the extension piece being secured to the engagement member. Desirably, the engagement member has the form of a flat plate and the extension piece extends substantially normal to this flat plate. Also desirably, the slot in the engagement member is a closed slot completely surrounded by the wall engaging surface. Preferably, the guard member further comprises a side piece attached to the engagement member adjacent the slot therein and extending rearwardly towards the saw body, adjacent a saw blade mounted on the blade attachment means, whereby the side piece acts as a guard for the saw blade.
Conveniently, the extension piece is provided with biasing means arranged to hold the engagement member in a central position when the engagement member is not in contact with a wall. This biasing means may comprise at least two springs disposed on opposed sides of the extension piece. The guard mounting means may comprises a shaft mounted on the saw body, the extension piece being mounted on the shaft, at least one of the saw body and the extension being pivotable relative to the shaft, and the biasing means being mounted on the shaft. In such an arrangement, conveniently the extension piece comprises a pair of spaced flanges, each of which has an aperture extending therethrough, and the shaft passes through these apertures.